JAG35 makes one of the cheapest wireless follow focuses in existence. Now they've improved upon their design and made the entire system much more durable. They also are introducing a clever follow focus that is friction based for newer lenses, but doesn't have to be mounted to the side like many other friction-based follow focuses. I talked with Jehu Garcia from JAG35 and he introduced those products, as well as a custom RED Scarlet/Epic rig and a new slider they are developing.
Jehu Garcia from JAG35:
The one big complaint about the JAG35 wireless follow focus has been the excessive noise. This has greatly been reduced, but if you watch the video, it is still much louder than a lot of other similar products out there. For the money though ($1300 for the one motor kit, $1800 for two), if you really need one, and your camera and sound will be more than a foot away from your talent, it's a great option. The friction follow focus is a really interesting design, and I have to say that it was very responsive when I was using it, and if I wasn't looking, I would think it was a traditional fully rigged follow focus. Many other fiction designs mount the knob off angle to the camera, but this design keeps it parallel to the lens, which is absolutely essential for a real working environment.
If you're looking for cheap rigs, JAG35 definitely has them. It also seems that they are getting into more high-end gear as they grow as a company - like their RED-specific rig, which looks good, but is likely out of the budget range of many of their consumers.